Tires have been retreaded for several decades according to a variety of methods. Retreading tires provides an economical way to gain additional use of a tire casing after wearing of the original tread and. According to one conventional method of retreading, sometimes referred to as precure retreading, a used casing is inspected for defects. The casing is then buffed to remove the tread and to produce a surface suitable for bonding a new tread layer. In addition to buffing, the shoulders of the casing may be trimmed to provide the proper crown width for the new tread. The buffed surface is again inspected for casing injuries. Next, skiving and filling of the casing are performed, as necessary, to restore the shape of the casing. Skiving includes the removal of damaged material from the casing before making a repair. Filling includes disposing repair gum into the skived out injured areas. Repair units are installed as necessary to restore integrity to the casing.
A bonding layer and a new tread layer are built about the circumference of the buffed surface. The bonding layer (e.g., layer of cushion gum) and tread layer are prepared. The ends of the bonding layer are cut at an appropriate length so that the bonding layer generally extends about the circumference of the casing. The bonding layer is disposed about the circumference of the buffed surface of the tire casing. The tread ends are prepared for building a tread splice. Preparation of the tread ends includes cutting the tread at an appropriate length to generally extend about the entire circumference of the casing, brushing a thin layer of tire cement on each tread end, drying the cement, disposing the ends of the tread in close proximity to one another, and mating the tread ends together to form a tread splice. A portion of bonding material is sometimes disposed between the leading edge and the trailing edge of the tread ends as an adhesive. The new tread layer is wrapped about the circumference of the tire casing over the bonding layer.
During the process of building, temporary fasteners (e.g., staples) hold the tread splice together. Each staple generally has a pair of prongs, where one prong is inserted into the trailing edge of the tread layer and the other prong is inserted into the leading edge of the tread layer to retain the tread ends in position until curing is complete.
A fabric wick material is then placed on the tread layer at a location remote from the tread splice. The wick is temporarily affixed with fasteners (e.g., staples) to the tread surface of the assembled tire. The wick permits the passage of air from the assembled tire to an exhaust fitting of an envelope. The wick is positioned between the tread and the envelope. Placement of the wick anywhere about the circumference of the tread layer, except directly over the tread splice, prevents the uncured bonding layer from plugging the wick. Plugging of the wick causes improper venting, which in turn results in a poorly bonded retreaded tire. A disadvantage of such conventional wicks is that it is difficult to determine when to replace the wick, which results in decreased wick effectiveness over time.
A wick liner (e.g., plastic film, rubber sheet) is used in conjunction with the wick to prevent the bonding layer from penetrating the wick during curing, which destroys the effectiveness of the wick. Plastic wick liners are disadvantageous because they permit the transfer of the woven pattern of the wick to the bonding layer. The transferred pattern creates a discontinuity in the appearance of the bonding layer. Rubber wick liners are disadvantageous because they create a noticeable "step" on the bonding layer caused by the thickness of the rubber wick liner.
Following the assembly of the tire casing, bonding layer, tread layer, wick liner, and wick material, the overall retreaded tire assembly is placed within a flexible rubber envelope. An airtight seal is created between the envelope and the bead of the tire using a curing rim, or sealing rings. The envelope includes an exhaust fitting (e.g., "valve" as the term is used in the retreading industry). The exhaust fitting permits bidirectional airflow during the curing process. Typically, the exhaust fitting is disposed at a location remote from the tread splice, but directly over the wick. The wick is disposed between the exhaust fitting of the envelope and the tread surface. Placement of the exhaust fitting over the wick prevents the tread from blocking the exhaust fitting during the curing process.
The enveloped tire assembly is then placed in a curing chamber (e.g., autoclave), and subjected to heat and pressure for a specified period. The chamber is heated to approximately two-hundred and ten degrees Fahrenheit (210.degree. F.) and pressurized to approximately eighty-five (85) psig. The exhaust fitting is connected to a hose that allows the pressure at the interior of the envelope to be controlled such that a pressure differential is created across the envelope. The combination of pressure and temperature over time cures the bonding layer, permanently mounting the new tread to the casing.
After curing, the sealing rings and the envelope are removed from the retreaded tire. The wick and staples are also removed from the retreaded tire. Typically, the staples are removed individually and fall to the floor of a work space. Removing the staples individually is labor intensive. Removing staples in this manner has the disadvantage of creating a cluttered work space that can potentially damage envelopes in the work space. Accordingly, it would be advantageous to provide a method and system to assist in the removal of air from an assembled tire during retread curing and to extract and retain temporary fasteners used during the curing of retreaded tires.